The present disclosure relates to an ink introduction method of introducing an ink into an inkjet recording head and an inkjet recording apparatus.
In the case where an inkjet recording apparatus or a recording head to be mounted in an inkjet recording apparatus is transported from a production site such as a factory with a flow channel within the recording head filled with an ink, the ink may deteriorate before the inkjet recording apparatus or the recording head is delivered to a user. Deterioration of an ink may hinder recording of a satisfactory image on a recording medium such as paper.
In the case where an inkjet recording apparatus or a recording head is transported with a flow channel within the recording head empty, an ink will for example be introduced into the flow channel within the recording head after the inkjet recording apparatus or the recording head is delivered to a user. In this case, however, the flow channel within the recording head is dry at the time of the ink introduction. In the dry flow channel, the ink shows poor wetting and spreading characteristics and tends to generate air bubbles therein. Air bubbles generated in the ink loaded in the flow channel within the recording head may hinder recording of a satisfactory image on a recording medium such as paper. The generation of air bubbles tends to occur particularly in a piezoelectric inkjet recording head.
When an ink is introduced into an empty recording head, therefore, an evacuation process to evacuate air bubbles is needed in the ink introduction. The need brings a concern that the time required for the ink introduction is increased by the time required for the evacuation process.
It is therefore desirable that prior to transportation of an inkjet recording apparatus or a recording head, a flow channel within the recording head is filled with a coloring material-free preservative solution. More specifically, the inkjet recording apparatus or the recording head is transported from a production site with the flow channel within the recording head filled with the preservative solution. The preservative solution in the recording head is replaced with an ink after the inkjet recording apparatus or the recording head is delivered to a seller or a user.
The preservative solution is required to have the following three functions.
(1) Introduction and diffusion facilitating function: A function of facilitating the ink to show good wetting and spreading characteristics in the flow channel within the recording head and facilitating the ink to diffuse well in the preservative solution in introduction of the ink into the recording head and replacement of the preservative solution in the recording head with the ink
(2) Aggregation preventing function: A function of preventing aggregation of a coloring component in the ink such as a pigment in introduction of the ink into the recording head and replacement of the preservative solution in the recording head with the ink
(3) Antifreezing function: A function of preventing freezing of the preservative solution
Of the three functions, the antifreezing function works to prevent a fine structure or a fine feature of a recording head, such as a flow channel having a fine step and a fine gap, from being damaged in a low-temperature environment. If a preservative solution that does not have the antifreezing function is loaded in a recording head, an aqueous component in the preservative solution may freeze and expand in a low-temperature environment and cause damage of a flow channel within the recording head. In the case of a piezoelectric inkjet recording head, the piezoelectric element thereof may be damaged. The antifreezing function contributes to prevention of damage of the fine structure or the fine feature due to a low-temperature environment. The antifreezing function is therefore particularly necessary in colder climates.
In order to impart the antifreezing function to the preservative solution, it is necessary to include a large amount of moisturizing agent in the preservative solution. The moisturizing agent has a relatively high specific weight. Inclusion of a large amount of moisturizing agent in the preservative solution therefore results in the preservative solution having a higher specific weight than the ink. Consequently, the ink is less diffusive in the preservative solution. In other words, the preservative solution has poor introduction and diffusion facilitating function. Having poor introduction and diffusion facilitating function, the preservative solution cannot facilitate ink introduction into a recording head. It is therefore difficult for the preservative solution to have both the antifreezing function and the introduction and diffusion facilitating function. The time required to replace the preservative solution with the ink increases with decreasing in the diffusivity of the ink in the preservative solution. As a result, the ink is more likely to generate air bubbles. Another concern is that the preservative solution may remain in the flow channel within the recording head for a long period of time.